A 15-year-old girl sits in high school English class when a text message pops up on her cellphone. It's from a boy sitting across the room. He hardly knows her, but he likes her. Here's how he chooses to get that message across:

Him: "So, are you good at hooking up?"

Her: "Um idk. I don't really think about that."

Him: "Well, I want my d--k in your mouth? Will you at least be my girlfriend."

It's the kind of scenario that's playing out among teens across America, illustrating an increasing confusion among boys about how to behave, experts say. In the casual-sex "hookup" culture, courtship happens by text and tweet. Boys send X-rated propositions to girls in class. Crude photos, even nude photos, play a role once reserved for the handwritten note saying, "Hey, I like you."

According to new research, boys who engage in this kind of sexualized behavior say they have no intention to be hostile or demeaning — precisely the opposite. While they admit they are pushing limits, they also think they are simply courting. They describe it as "goofing around, flirting," said Catherine Steiner-Adair, a clinical psychologist and school consultant who interviewed 1,000 students nationwide for her new book, "The Big Disconnect: Protecting Childhood and Family Relationships in the Digital Age."

How the hookup culture affects young people has long been debated and lamented, in books and blogs, among parents and teachers. A general consensus is that it harms girls, although some have argued that it empowers them. The effect on boys, however, is less often part of the discussion.

Conventional wisdom tends to oversimplify the situation to something along the lines of: Boys get to have sex, which is really all they want. They are seen as predators, and girls, their prey.

Reality is far more complex than this, in ways that can affect young men socially and emotionally well into adulthood, according to Steiner-Adair. It's "insufficient, superficial and polarizing when boys simply get cast as aggressors and girls as victims," she said. In her view, girls can certainly suffer negative consequences from the hookup culture. Her point is: Boys can, too. "It's such a bad part of our culture to think that boys aren't also harmed," she says. "We are neglecting the emotional lives of boys."

In interviews and focus groups, Steiner-Adair talked with boys and girls ages 4 to 18 at suburban public and private schools, with consent from parents and schools, about their relationships and influences. Kids from the fourth grade and up shared their private texts and Facebook posts, unveiling the dating landscape. In one case, a boy sent a naked snapshot of himself to his girlfriend, with a suggestive caption. The girl, who had never seen her boyfriend naked, was shocked, and said she felt the relationship had suddenly lost its innocence. "I was so mad about that," she said. The girl's reaction, in turn, surprised the boy. He really liked her. His behavior, said Steiner-Adair, was "aggressive in a way that boys don't understand."

Steiner-Adair also saw the string of texts between the 15-year-old girl in English class and her suitor. The girl described the conversation as "a stupid, disgusting exchange," adding that it was "typical for the boys at our school." Still, the girl became intrigued when the boy revealed in a subsequent note that he liked her. The girl wondered if she should tell him how his initial approach had offended her. Then she started to cry, questioning whether it was worth the effort.

Teenagers have never been known for their social grace. But this generation is navigating adolescence with a new digital tool kit — Facebook, Twitter — that has the unintended side effect of subtracting important social cues, according to Steiner-Adair. Nuance and body language are lost in translation.

She also noted the influence of online porn. Students across the country asked Steiner-Adair about graphic images they had seen. One boy said, "I don't get it — why would a woman get turned on by being choked?" A girl asked her if it was normal to have anal sex.

Another boy showed her pornographic notes that two of his friends had secretly sent to a girl from his own Facebook page, including, "Your challenge is to go for weeks without d--ks in all four of your holes." When the boy found out about the prank, he wasn't upset, but amused. "This is just my friends being idiots, basically," he said. "They were just trying to be funny." Steiner-Adair asked why the exchange had turned so nasty and the boy said, "It didn't turn nasty. That's the norm for our generation."

To be sure, some boys have always been crude. The new extremes, said Steiner-Adair, can be damaging. Boys don't benefit, she said, from learning to be demeaning toward girls or to treat them as sexual objects. She said boys often expressed a desire for a deeper connection with girls, but felt confused about how to make it happen. They are "yearning for intimacy that goes beyond biology," she said. "They just don't know how to achieve it."

Andrew Smiler, a developmental psychologist, agrees. He examined some 600 studies on masculinity, sex and relationships for his book "Challenging Casanova," concluding that most young men are more motivated by love than sex. Pop culture helps spur the disconnect between what young men want and how they often act, he argues, citing as an example the show "Two and a Half Men." "The jerk gets all the laugh lines," he said. "The nice guy always looks like a sap."

That theory is debated. Steven Rhoads, a professor who teaches a class on sex differences at the University of Virginia, said he analyzed decades worth of research on sexuality and biology for his book "Taking Sex Differences Seriously" to conclude that men and women are "hardwired" differently. Hookups have deeper psychological costs for women, he said, noting that anecdotes from his students back up the research: Female students often tell him they are hurt by casual sex in a way that male students are not. The boys don't know it, he said, because the girls don't want to tell them.

For boys and girls alike, crucial lessons in how to relate to each other are getting lost in the blizzard of tweets and texts, experts say. The cues kids would pick up from a live conversation — facial expressions, gestures — are absent from the arm's-length communications that are now a fixture of growing up. The fast-paced technology also "deletes the pause" between impulse and action, said Steiner-Adair, who calls texting the "worst possible training ground" for developing mature relationships. Dan Slater, the author of "Love in the Time of Algorithms," agrees. "You can manage an entire relationship with text messages," he said, but that keeps some of the "messy relationship stuff" at bay. "That's the stuff that helps people grow up," he added.

The key to developing solid relationships lies partly in early education, said Steiner-Adair. To that end, some schools are launching classes focused on social and emotional issues, with teachers talking about gender, language, social media and healthy relationships.

Also critical, according to Steiner-Adair, is family time spent away from screens. In her research, teens often said their parents were embroiled in work or personal interests and simply not available. Some parents said they were intimidated by their children's complaints and exploits, and didn't want to seem ignorant or helpless. The heart of the matter for families, she said, is good old-fashioned talking — the kind you do face to face.

Abigail Pesta is an award-winning journalist who has lived and worked around the world, from London to Hong Kong. She has written for The Wall Street Journal, The New York Times, Cosmopolitan, Marie Claire and Newsweek. Follow her at @AbigailPesta.